batman-adv: Fix use of seq_has_overflowed()

net-next commit 6d91147d183c ("batman-adv: Remove uses of return value
of seq_printf") incorrectly changed the overflow occurred return from
-1 to 1.  Change it back so that the test of batadv_write_buffer_text's
return value in batadv_gw_client_seq_print_text works properly.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/batman-adv/gateway_client.c

@@ -601,7 +601,7 @@ static int batadv_write_buffer_text(struct batadv_priv *bat_priv,
 		   gw_node->bandwidth_down % 10,
 		   gw_node->bandwidth_up / 10,
 		   gw_node->bandwidth_up % 10);
-	ret = seq_has_overflowed(seq);
+	ret = seq_has_overflowed(seq) ? -1 : 0;
 
 	if (curr_gw)
 		batadv_gw_node_free_ref(curr_gw);